They probably should have kept this plan under their hat until January.
Why give the opposition additional time to try to stop it?
1) They knew Bush wouldn't do it.
2) They are terrified Trump might do it, so they are already preparing to stop it.
3) The benefit in rallying the base from announcing it now and making it a campaign theme is greater than the risk of alarming the soon-to-be deposed villains...who are already alarmed.